I've heard that Meyer lemons are also smaller, rounder, and not as acid as regular lemons -- but the info I've been able to discover so far suggests that Meyer lemons are a hybrid between lemons and mandarins (or possibly tangerines). They're from China, while the sweet lemon (a distinct species, C. limetta) is from the Middle East.
http://www.hort.purdue.edu/newcrop/morton/lemon.htmlhttp://www.hort.purdue.edu/newcrop/tropical/lecture_32/citrus_R.htmlhttp://www.fourwindsgrowers.com/lore/meyer.htmlhttp://www.tradewindsfruit.com/citrus.htmI had a chance to taste it last night. Thinner skin and easier to peel than most lemons, and it doesn't taste acidic or even "lemony". It's got a kind of bitter aftertaste, though I'm still trying to pin down what the main taste is like -- kind of medicinal? It's certainly different from anything I've had before -- not unpleasant though.
I'm thinking that the juice might work as a dressing, on a mild-tasting green like most kinds of lettuce.